1. Field of the Disclosure
This disclosure relates to a flat display device unified with a touch panel which is adaptive to improve their reliability.
2. Description of the Related Art
Touch panels have been used mainly in manufacturing systems, game appliances, KIOSKs, POSes, medical equipments, and so on, instead of input devices such as keyboard and mouse. The touch panel is mounted to the display screen of an output device and allows users to input data in a variety of ways in such a manner that the user views image information on the display screen of the output device and directly presses designated positions on the display screen.
The touch panels are classified into capacitive type, resistive type, and so on. The capacitive touch panels repeatedly charge and discharge electric-charges to one transparent conduction film or glass, and enable an arbitrary quantity of electric-charges to be stored at a contact point on the film or glass contacted with a stylus which is shaped like a pen. The stored electric-charge quantity at the contact point depends on a coupling capacitance of the stylus and the transparent conduction film or glass. Also, the capacitive touch panels read out the stored electric-charges at the contact point through four input nodes and derive coordinates from those. In these capacitive touch panels, electric power must be applied to the stylus.
The resistive touch panels apply a voltage between two conduction layers facing each other, read out a voltage or current variation at a contact point at which the conduction layers come into contact with each other when pressed by the user, and then derive x and y coordinates from the voltage or current variation. In order to read out the voltage or current variation, the resistive touch panels include electrodes such as bus-bars. The flat display devices. including the resistive touch panels, can also be classified into a touch panel-unification type and a touch panel-addition type according to the manner in which the touch panel is combined with the display device.
The flat display device unified with the resistive touch panel will now be described in detail with reference to accompanying drawings. FIG. 1 is a plane view of a flat display device unified with a resistive touch panel according to the related art. FIG. 2 is a cross sectional view showing a flat display device with a touch panel taken along line I-I′ in FIG. 1.
Referring to FIGS. 1 and 2, the flat display device, unified with the touch panel according to the related art, includes a liquid crystal display panel 10 displaying an image (or a picture), a touch panel 20 disposed on the liquid crystal display panel 10, and a printed circuit board (PCB) 30 which is loaded with a drive portion that drives the liquid crystal display panel 10 and the touch panel 20. Although it is not shown in the drawings, polarizer films dispersing lights are disposed on the upper and lower surfaces of the liquid crystal display panel 10.
The liquid crystal display panel 10 includes a color filter substrate 10a and a thin film transistor substrate 10b which are combined in the center of a liquid crystal layer 10c interposed therebetween. In the thin film transistor substrate 10b, gate lines 12 receiving scan signals from the exterior and data lines 15 receiving data signals are formed to cross each other. The thin film transistor substrate 10b includes a gate driver 13 at one ends of the gate lines 12, and a data driver 16 at one ends of the data lines 15. The color filter substrate 10a and the thin film transistor substrate 10b are combined with each other by means of a sealant 17 disposed on their edges.
The touch panel 20 includes a resistive sheet 23 formed from a transparent material and functioning a resistive film, a first transparent conduction film 24 formed on the lower surface of the resistive sheet 23, a second transparent conduction film 26 formed on the upper surface of the color filter substrate 10a, and spacers 25 constantly separating the resistive sheet 23 and the color filter substrate 10a from each other by a fixed distance.
In this manner, the liquid crystal display panel 10 and the touch panel 20 are independently configured. Due to this, a first malleable circuit substrate 11 connected to the liquid crystal display panel 10 and a second malleable circuit substrate 21 are included, in order to drive the liquid crystal display panel 10 and the touch panel 20. These first and second malleable (or flexible) circuit substrates 11 and 21 are connected to second and third connectors 31 and 33 on the drive PCB 30, respectively. The drive PCB 30 includes a control integrated circuit (IC) chip, a power supply portion, several wiring patterns, and so on, which are used for driving the liquid crystal display panel 10 and the touch panel 20 to interact with each other.
However, since the contact area (width) d1 of the first connector 22 and the touch panel 20 is narrowed, the flat display device unified with the touch panel according to the related art deteriorates the reliability of electric connection between the first connector 22 and the touch panel 20. Moreover, there is a problem in that a connection defect between the touch panel 20 and the first connector 22 is frequently caused by impacts which are capable of being generated during assembly of the flat display device unified with the touch panel, for example, by shaking generated upon feeding of the flat panel device.